Oncostatin M (OM) is a pleiotropic cytokine produced late in the activation cycle of T-cells and macrophages. Initially reported in 1986 (Zarling et al., Proc. Natl. Acad. Sci. U.S.A. 83: 9739-9743 (1986)), Oncostatin M has been extensively characterized and numerous activities ascribed to it. It was originally isolated from conditioned media of a phorbol ester-treated histiocytic lymphoma cell line, U937, based on the ability to inhibit the growth or development of a human melanoma cell line. Cloning of a cDNA for Oncostatin M showed that it encodes a 227 amino acid polypeptide (Malik et al., Mol. Cell. Biol. 9: 2847-2853 (1989)) which is structurally and functionally related to the family of hematopoietic and neurotrophic cytokines whose members include leukemia inhibitory factor (LIF), interleukin-6 (IL-6), interleukin-11 (IL-11), ciliary neurotrophic factor (CNTF), and cardiotrophin. Rose and Bruce, Proc. Natl. Acad. Sci. U.S.A. 88: 8641-8645 (1991).
Oncostatin M has been found to bind to three cell surface receptors. It binds to a gp130 polypeptide, also known as the IL-6 signal transduction subunit, with a low affinity, but the interaction, by itself, appears to be nonfunctional (Gearing, New Biol., 4:61 (1992)). In a second, intermediate affinity interaction, Oncostatin M and LIF have been shown to compete for binding to a receptor composed of the low-affinity LIF receptor and gp130. This intermediate affinity receptor complex is capable of signalling and exerting biological effects in vitro. Although this receptor complex is shared by the two cytokines, the affinity of interaction and biological signals delivered by each of the cytokines are distinct. The third receptor recognized by Oncostatin M is a high affinity receptor that is not known to bind to other cytokines. It is believed responsible for mediating those properties which are unique to Oncostatin M (Linsley et al., J. Biol. Chem. 264: 4282-289, (1989); Thomas et al., J. Biol. Chem. 269: 6215-6222 (1994)). The high affinity Oncostatin M receptor is composed of gp130 and an affinity-converting subunit (Moseley et al., J. Biol. Chem. 271:32635-43 (1996)) that has been cloned. The affinity-converting subunit is required for high affinity and functional ligand-receptor binding.
The overlapping properties of the IL-6-like cytokines presumably arise from the presence of gp130 in each of their receptors. However, there are unique properties and signal transduction pathways which are engaged when these receptors bind their ligands. In vitro, Oncostatin M acts on a wide variety of cells and elicits a multitude of biological responses, including growth modulation, leukemia cell differentiation, LDL receptor up-regulation, stimulation of plasminogen activator, induction of hematopoietic factors, induction of acute phase proteins, inhibition of embryonic stem cell differentiation, and induction of tissue-inhibitors of metalloproteinases-1. Of these properties, many are shared with other related cytokines, though others as yet have only been ascribed to Oncostatin M.
The in vivo toxicology and pharmokinetics of Oncostatin M have been evaluated. Recombinant Oncostatin M expressed in CHO cells has been administered to normal or myelosuppressed mice without lethality and with minimal weight loss. Oncostatin M administered intravenously is rapidly (.about.10 minutes) cleared to the liver and kidney; at one hour &lt;3% remains in these organs, suggesting that it is metabolized. Injection of mice with Oncostatin M results in increased levels of circulating platelets while there is no effect on red or white blood cell levels. A similar effect has been found in a non-human primate (i.e. cynmolgus and Rhesus monkey) where there is a dose-dependent increase in circulating platelet levels.
Oncostatin M has been reported to induce activity of acute phase proteins in hepatocytes (Richards et al., J. Immunol. 148:1731-1736 (1992), and thus has been proposed to be administered therapeutically to stimulate acute phase responses and treat disease states or injuries that result in either an inflammatory response or tissue degeneration at an afflicted site. Shoyab et al., PCT/US93/07326, incorporated herein by reference.
Inflammation occurs in response to numerous conditions including physical injury, tumor growth in a tissue, chemical damage to a tissue, and bacterial, parasitic, fungal or viral infection. Inflammation results in both local and systemic effects. Representative effects that can occur at a site of injury or disease are increased vascular permeability, release of degradative enzymes including metalloproteinase, migration to the affected site by leukocytes, neutrophil burst response to destroy invading cells, and the secretion of cytokines. Important systemic effects include pain, fever, and the acute phase response of the liver.
The acute phase response involves the production of a broad spectrum of substances acting, in general terms, to regulate the cells and enzymes that are responsible for inactivating the causative agent(s) of the inflammatory process. Thus, the acute phase proteins form a "feedback loop" that minimizes adventitious tissue damage and regulates the eventual return to homeostasis. The feedback process is pleiotropic and includes the production of anti-inflammatory cytokines, inhibitors of proinflammatory cytokines and inhibitors of numerous degradative proteases that are active in inflammation.
The temporal expression of cytokines reflects their respective roles during progression and resolution of an inflammatory response. TNF-alpha, for example, is rapidly induced following tissue injury or infection, triggering an inflammatory response that is amplified by the induction of IL-1-alpha and -beta. As feedback to limit and subsequently attenuate inflammation, IL-6, protease inhibitor proteins, and corticosterone are induced to shift the balance to wound repair and suppression of inflammation.
What is needed in the art is a means to control specific inflammatory conditions by enhancing the anti-inflammatory feedback loop. The process should work in conjunction with naturally occurring cytokines to enhance the negative feedback of proinflammatory cytokine production, in addition to inhibiting the biological effects of the proinflammatory molecules. Moreover, the therapeutic process should be capable of having a direct effect on epithelial cells and fibroblasts to minimize the inflammatory process surrounding these cells, particularly those epithelial cells of the synovium, lungs, and the gastrointestinal tract which are particularly susceptible to inflammatory disease and damage induced by radiation and cytotoxic cancer therapies. Quite surprisingly, the present invention addresses these and other related needs.